TRANSIT CONFIRMATION AND IMPROVED STELLAR AND PLANET PARAMETERS FOR THE SUPER-EARTH HD 97658 b AND ITS HOST STAR
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Citation Van Grootel, V., M. Gillon, D. Valencia, N. Madhusudhan, D. Dragomir, A. R. Howe, A. S. Burrows, et al. “TRANSIT CONFIRMATION AND IMPROVED STELLAR AND PLANET PARAMETERS FOR THE SUPER-EARTH HD 97658 b AND ITS HOST STAR.” The Astrophysical Journal 786, no. 1 (April 8, 2014): 2. © 2014 The American Astronomical Society
As Published http://dx.doi.org/10.1088/0004-637X/786/1/2
Publisher IOP Publishing
Version Final published version
Citable link http://hdl.handle.net/1721.1/94587
Terms of Use Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The Astrophysical Journal, 786:2 (11pp), 2014 May 1 doi:10.1088/0004-637X/786/1/2 C 2014. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
TRANSIT CONFIRMATION AND IMPROVED STELLAR AND PLANET PARAMETERS FOR THE SUPER-EARTH HD 97658 b AND ITS HOST STAR
V. Van Grootel1,10, M. Gillon1, D. Valencia2, N. Madhusudhan3, D. Dragomir4,5,A.R.Howe6, A. S. Burrows6, B.-O. Demory3,7,D.Deming8, D. Ehrenreich9, C. Lovis9, M. Mayor9, F. Pepe9, D. Queloz3,9,R.Scuflaire1, S. Seager7, D. Segransan9, and S. Udry9 1 Institut d’Astrophysique et de Geophysique,´ UniversitedeLi´ ege,` 17 Alleedu6Ao´ ut,ˆ B-4000 Liege,` Belgium; [email protected] 2 Department of Physical and Environmental Sciences, University of Toronto, 1265 Military Trail, Toronto, ON, M1C 1A4, Canada 3 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 4 Las Cumbres Observatory Global Telescope Network, 6740 Cortona Dr. Suite 102, Goleta, CA 93117, USA 5 Department of Physics, Broida Hall, UC Santa Barbara, CA 93106, USA 6 Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA 7 Department of Earth, Atmospheric and Planetary Sciences, Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA 8 Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA 9 Observatoire de Geneve,` UniversitedeGen´ eve,` 51 Chemin des Maillettes, CH-1290 Sauverny, Switzerland Received 2014 January 2; accepted 2014 February 25; published 2014 April 8
ABSTRACT Super-Earths transiting nearby bright stars are key objects that simultaneously allow for accurate measurements of both their mass and radius, providing essential constraints on their internal composition. We present here the confirmation, based on Spitzer transit observations, that the super-Earth HD 97658 b transits its host star. HD 97658 is a low-mass (M∗ = 0.77 ± 0.05 M) K1 dwarf, as determined from the Hipparcos parallax and stellar evolution modeling. To constrain the planet parameters, we carry out Bayesian global analyses of Keck–High Resolution Echelle Spectrometer (Keck-HIRES) radial velocities and Microvariability and Oscillations of STars (MOST) and = +0.83 = +0.098 Spitzer photometry. HD 97658 b is a massive (MP 7.55−0.79 M⊕) and large (RP 2.247−0.095R⊕ at 4.5 μm) super-Earth. We investigate the possible internal compositions for HD 97658 b. Our results indicate a large rocky component, of at least 60% by mass, and very little H–He components, at most 2% by mass. We also discuss how future asteroseismic observations can improve the knowledge of the HD 97658 system, in particular by constraining its age. Orbiting a bright host star, HD 97658 b will be a key target for upcoming space missions such as the Transiting Exoplanet Survey Satellite (TESS), the Characterizing Exoplanet Satellite (CHEOPS), the Planetary Transits and Oscillations of stars (PLATO), and the James Webb Space Telescope to characterize thoroughly its structure and atmosphere. Key words: binaries: eclipsing – planetary systems – stars: individual (HD 97658) – techniques: photometric – techniques: radial velocities Online-only material: color figures, machine-readable table
1. INTRODUCTION Absil et al. 2013; Kuzuhara et al. 2013). Transiting super-Earths around bright nearby stars are therefore essential for shedding Among the diversity of the exoplanetary population, the class light on their true nature and origin. of the so-called “super-Earths,” with a mass of a few Earth HD 97658 is the second-brightest (V = 7.7, K = 5.7) masses, is of utmost interest. First, they do not exist in the solar host star found to be transited by a super-Earth (the bright- system, leaving us with only extrasolar planets for detailed est being 55 Cnc; Winn et al. 2011; Demory et al. 2011). studies. Second, they seem to be extremely common in the HD 97658 b was detected from radial velocity (RV) mea- Galaxy (Fressin et al. 2013; Petigura et al. 2013;Howard2013). surements with Keck–High Resolution Echelle Spectrometer Third, a wide variety of interiors are theoretically possible (Keck-HIRES) spectroscopy, with a minimum mass MP sin i = for a small range of radii (1